Circuit interrupter



March 25, 1952 A. w. EDWARDS CIRCUIT INTERRUPTER Filed sept. 29, 1949INVENTOR Andrew W. Edwards. 48 BY '06 6i i! ATTORNEY WITNESSES:

Patented Mar. 25, 1952 CIRCUIT INTERRUPTER Andrew W. Edwards, EastMcKeesport, Pa., assignor to Westinghouse Electric Corporation, EastPittsburgh, Pa., a corporation of Pennsylvania Appcationseptember 29,1949, serial No. 118,500

l 14 Claims.

This invention relates generally to electric circuit interrupters, andmore particularly to such interrupters of the type having means forelongating the arc during a circuit interrupting operation.

inasmuch as a circuit interrupter may be called upon to interruptcurrents which vary widely in magnitude, it has been the practice ininterrupter design to effect some compromise in their construction inregard to ability to interrupt are given magnitude of current, becausethe most eicient design for a given current magnitude is quite differentfrom that for another current magnitude. Such design compromises aredictated by economic considerations as it has been generally thoughtimpractical from a cost standpoint to provide at any given location, aninterrupter entirely suited for every possible value of current whichmight be encountered at that location.

One such design feature which has been the subject of compromise is thespeed at which the arc terminals are separated during circuitnterruption. For high current interruption it is` desirable to have arelatively low speed at which the are terminals separate because therate of energy input to the are is high enough so that the arc will beextinguished at the rst or second current zero, and yet by keeping thearc length short at that time, it is possible to limit the total energyinput to the arc and the arc voltage. For the interruption of lowcurrents, however, it is desirable to separate the arc terminals at ahigh speed because the energy input rate of such arcs is not important,but the arcs. must be quite. long before they can be extinguished.

Accordingly, one object of this invention is to provide a circuitinterrupted having means for separating the arc terminals at a speedwhich varies generally inversely with the magnitude of current beinginterrupted.

More specically, it is an object of this invention to provide high speedarc terminal separating means for a circuit interrupter, with means forbraking separating movement dependent on the magnitude of current beinginterrupted.

These and other objects of this invention will become more apparent uponconsideration ofthe following detailed description of preferredembodiments thereof, when taken in connection with the attached drawing,in which:

Figure 1 is a side elevational view partially in section, showing a fuseembodying this invention;

Fig. 2 is an enlarged longitudinal sectional view of the rell unit forthe fuse shown in Fig. 1;

Fig. 3 is a transverse cross-sectional view taken substantially on theline III-III of FigfZ;

Fig. 4 is a transverse cross-sectional view taken through a modifiedform of fuse rell at substantially the same point that the section ofFig. 3 is taken; and

Fig. 5 is a side elevational View, partially in section. of a circuitbreaker embodying this invention.

The circuit interrupter disclosed in Figs. 1 to 4 embodying thisinvention, is particularly illustrated as comprising afuse of thegeneral type shown in J. M. Wallace Patent No. 2,276,899, issued March17, 1942, to the same assignee as this invention. This type of fuse,generally, is contained in a weatherproof tube 2 o1 insulating material,such as porcelain or the like, and containing an inner tube 4 also ofinsulating material, but which need not be weatherproof in character,such, for example, as ber or the like. The inner tube 4 has a topcontact cap 6 threadedly mounted on the upper end thereof, with this caphaving an integral flange 8 at its inner end, with a washer I0 0f aresilient packing material, such, for example, as rubber or the like,being interposed between flange 8 and the upper end of outer tube 2. Abottom terminal ferrule I2 is threadedly mounted on the lower end ofinner tube 4, and a washer I4 of a material similar to washer I0 isinterposed between the upper end of ferrule I2 and the lower end ofouter tube 2, so that the latter may be clamped between ferrule I2 andtop cap 6.

For the purpose of mounting the fuse o'n a line terminal support or thelike, bottom terminal ferrule I2 may be provided with a plurality ofintegral mounting and positioning lugs I6 and I8 (only one of each beingshown) for engagement with the line terminal structure. To enablehandling of the fuse, the upper terminal cap 6 may have an integralextension 20 for pivotally supporting a hook-eye 22, in which ahook-stick or other operating member may be inserted.

The fuse further includes a renewable fuse unit 24 mounted within theholder structure comprising inner tube 4, outer tube 2, top cap 6 andferrule I2. The fuse unit 24 has its own supporting tube 26 ofinsulating material, which may be of fiber or the like, with this tubebeing filled with a gas evolving `material 28, such, for example, asboric acid. The filling material 28 is retained within tube 26 by a topplug 30 of insulating material, preferably a molded insulating material,which is threaded into the upper end of tube 26, and may have a washer32 also in position' 3 of a similar insulating material located at theinner side of plug 30. A bottom plug 34 is held in position within thelower end of tube 26 by a bottom contact ferrule 36 which is threaded0nto the lower end of tube 26. If desired, a washer 38 may be interposedbetween an internal shoulder provided integral with ferrule 36 and thelower end of refill tube 26. Y

The filler material 28 is provided with a relatively large central bore40, and with a smaller bore 42 at one side. ends of bores 40 and 42 bymeans of an oval- Access is had to the upper lrenewable fuse unit, andthen through this rod, iiexible strip 50, fusible material 52, flexiblestrip 54,"botto'm`contact ferrule 36 to bottom terminal shaped opening43 providedi-n plug 38, with the lower ends of these bores opening intoan outwardly ared bottom outlet portion 544,. whichtion shown in Fig. v2by a fusible connection tol contact ferrule 36 comprising a strip of'conf ducting material 5 0 secured to the lower end of rod 48, and joinedby a mass of fusible Inaterial 52 to a second conducting strip 54 whichvis in turn secured to contact ferrule 36, as by a A strain element 58alsov connects4 screw 56. the lower end of rod 48 to contact ferrule 36,being also secured to the ferrule by screw 55.

Both strips 50 and 58 are brought together andv secured in aslotprovided in the lower end or rod 48, for example as by solder or thelike. Strain element 58 is also of an electrical conducting material,but is of a material having higher resistance than either strips 58 or54,l

or the fusible material 52. Thus, the main cur-v rent path-between rod48v and contact ferrule 35 will be that of lowest resistance,comprisingstrip 50, fusible mass 52 and strip 54.

Small bore 42 in ller material 28 contains' one wire 50 secured to theupper end of rod 48,.

as by being looped about a cross-pin 62 passing through the upper end ofrod 48, and this wire extends downwardly in bore 42 and overlaps theupper end of a second wire 64 which has its lower end secured betweenwasher 38 and bottom plug 34, by contact ferrule 36. It will thus beobserved that-there are two parallel conductingv paths between the upperend of rod 48 and contact ferrule 36, with the lower resistance 4pathbeing through large bore 40.

Renewable fuse unit 24 is adapted to be.mount-. ed in the fuse holdershown in Fig. l by inserte;

ity through the open lower end of the fuse holder until contact ferrule36 engages an inl tegral internal shoulder 66 on holder terminal. Thefuse unit 24 is held at this Aposi- .v tion by a threaded sleeve 68which is threaded-- errule I2.

into the lower end of holder ferrule I2 to clamp-V contact errule 36 ofthe fuse unit'against shoul der 66 of ferrule l2.l A head 10 issecuredtothe upper end of rod 48 when the fuse unitrZ is mounted in a fuseholder, as shown in-lig.' 1.,: and head 'Hl forms one anchor pointv foral coiled tension spring 12 stressed between head.VV 'i8 and an upperhead 14 which has a reduced;

threaded extension extending through a central opening in cap 6 and heldin position at the upper end of the holder by a cap nut 76. Head Hi onthe upper end of rod 48 for the fuse uniti,

24de vpreferably electrically connectedif he'ai '-ferr'u1e.-l;2of theholder. Accordingly, upon any a'excesscurrentow, fusible material 52will be melted,.and`since strain element 58 is disposed at an angle,tension spring 'l2 will exert a force component onfusible .material 52in a direction transversel tothe longitudinal axis of the fuse so that:as-'soon as the fusible material 52 softens,

it will be separated by this force component. The excessA current willthen substantially all pass through strain element 58 which will bequickly melted to release rod 48 for movement upwardly through itsbore48 by spring 12. As rod 48 moves upwardly, it also carries wire 60upwardly through its bore 42, with the first part of its movement havingits lower end in overlapping relationv to the vupper end of wire 64, andfinally separating these two wires.

'I'he difference in operation Von high and low currents is due to thefact thatthe circuit is rstbroken by fusion of fusible material 52 andstrain element 58, whereupon current now passes to thecircuit throughoverlapping wires 60 and 64' in the small bore 42. If the current beinginterrupted is cfa relatively low value, the arc formed upon fusion ofwire 6B, or in case these wires are not fused by actual separationthereof, is confinedin small bore 42 where it is most efficientlyextinguished due to the fact that it is in closer proximity to thegas-evolving material. However, if the current being interrupted is of arelatively high value, the small wires 60 and 64 will vfuse, and theresulting arc in bore 42 will haVuCh-a Ahigh are voltage due to thesmall lateral 'dimension of this bore that it will substantiallyinstantaneously transfer to large bore 46 and restrike from the lowerend of rod 48 to bottom contact ferrule 36, or any unfused remnants of`strips 50 and 54 and will eventually be extinguished in this bore 40.'

The present practice in fuses of this type which are employed iny highpower circuits employs rela` tively large masses as part of the assemblywhich must be moved by spring 'l2 in moving rod 48 upw'ardly'in ordertoobtain high interrupting ability.""'I he reason for, this practice isthat the use voi" such large masses having relatively high inertiac'orres'pondinglyreduces the velocity of upward travel of rod 48 Lduringthe early part of its movement after it is released at its lower end.'This 'prevents excessive lengthening of the arc prior to the firstcurrent zero, when such highlcurrent arcs are usually extinguished, and

' consequently keeps to a minimum the arc voltage and attendant highenergy which may cause V*forces high enough to rupture the fuse holder.

While such provision of slow initial travel of rod 48 vachieves itsobjective and is thus advantageous for the interruption of high currentarcs. it works to disadvantage during interruption of low Acurrent arcs,because the energy input rate ofsuch low-current arcs-is not important,but

Qn the; other hand inward-must. be lengtheeed.

as rapidly as possible to achieve early interruption of the are at anearly current zero.

This invention achieves efficient interrupting ability on both high andlow currents by introducing a semicircular permanent magnet 80, whichmay be imbedded in top plug 30 of re'iill unit 24 during the process ofmolding this plug. It will be observed that due to the particularposition of permanent magnet 88, a magnetic .field passes through rod48. When current iiows through the arcing rod, the reaction between thefield produced by this current about conductor 48, with the magneticiield of magnet 80, causes the rod 48 to move against one side or theother of the opening through washer 32, depending on the direction ofcurrent iicw through rod 48. On

high values of alternating current the rod will usually engage but oneside of the opening through washer 32 because the arc is usuallyextinguished at the rst current zero. On lower values ofalternating'current the rod may oscillate from side to side of theopening through washer 32 with each reversal of current now. On lowcurrents, the force with which rod 48 engages the side of the opening inwasher 32 is not large, so any braking action on upward movement of therod 48 under the innuence of coil spring 12 is very small. However, onhigh currents, the force urging the rod against the side of the openingin washer 32 is quite large, and the desired reduction in velocity isthus obtained to enable more eiiicient interruption of such largecurrent arcs. At the same time during inter ruption of lower currents,the movement of rod 48 is substantially unimpeded, and it will move veryquickly to thus most eiiiciently extinguish such low current arcs.Depending upon the direction of current iiow through rod 48, thelefthand side of opening 43 in plug 30 may assist Washer 32 in thisfrictional rubbing engagement. The retarding action on higher currentsis due to the friction between rod 48 and the material of plug 30 andwasher 32, and this retarding action may be enhanced by the use of afriction brake material in the manufacture of plug 30 and washer 32,such, for example, as asbestos brake lining material commonly used onautomobile brake shoes.

Even higher retarding frictional forces on high currents .duringmovement of rod 48 may be obtained by employing an inductively operatedelectromagnet in place of the permanent magnet 80, and such amodification is shown in Fig. 4 of thedrawing. This figure shows a plug|06 which may be of an insulating material like plug 30, and havingimbedded therein a semicircular bar |08 .of magnetic material, such, forexample, as soft iron or the like. A conductor yis also preferablyimbedded in the material of plug |06, and comprises one or more turnsabout the central axis of the fuse, with a number of turns in aclosedcircuit about magnetic bar |08, as shown at ||2. The operation ofthe electromagnetic braking means shown in Fig. 4 is exactly the same asthat of the permanent magnet shown in Figs. 2 and 3, except that muchhigher braking forces can be obtained as the value of current beinginterrupted increases due to the stronger magnetic field, as well as thehigher current through such field.

The invention is illustrated in Fig. of the drawing as applied to acircuit breaker which has a supporting tube 82 of an insulatingmaterial, such as fiber or the like, with an upper terminal ferrule 84secured to the upper end of tube 82,

and a lower terminal cap 86 threaded on the lower end of tube 82.Supporting tube 82 of the circuit breaker may be filled with an arcextinguishing material, such as the material 28 shown in Fig. 2, andthis material may be in the form of blocks 88 stacked inside tube 82,with each block having a central opening forming a substantially centralbore 89. A contact rod 90 is adapted in the closed position of thecircuit breaker to extend through bore 89 With the upper end thereofbeing engaged at opposite sides by contact fingers 92 mounted in upperterminal ferrule 84. The lower end of contact rod 90 is provided with ahead 94 secured thereto, with the head being electrically connected tobottom terminal cap 86 by a flexible conductor 96. A coil compressionspring 95 is located between head 94 of contact rod 90 and bottomterminal cap 86 to bias the rod downwardly for circuit opening movement.

Contact rod 90 is adapted to be held at the closed circuit positionshown in Fig. 5 with spring 95 in compressed condition by a latch lever98 having a latching portion adapted to engage head 94. Latch lever 98is preferably in the form of a bell crank lever having an armatureportion |82 located beneath a solenoid coil |04. Latch lever 98 ispreferably pivotally mounted at an intermediate point on a bracketsecured to lower terminal cap 88, as at |00.

In the closed circuit position of the circuit breaker shown in Fig. 5,the circuit extends from terminal ferrule 84 at the top of the breakerthrough contact fingers 92 to contact rod 90, and then by way offlexible conductor 96 to bottom terminal cap 86. Solenoid coil |04 maybe connected in series in the same circuit, or it may be energized fromanother source, but in any case when it is energized sufficiently toattract armature |02, latch 98 will be released to thus release contactrod 90 for movement by spring 95 downwardly, to draw an arc between theupper end of the rod and ferrule 84 and rapidly elongate such arcthrough bore 89 in the arc extinguishing material.

In order that most eiiicient arc extinguishing action may be had ininterrupting currents of low value as well as currents of high value, it

will be observed that a plug ||4 is provided in' tube 82 at the bottomthereof, preferably constructed of a molded insulating material similarto the material employed for plug 30 in the embodiment of the inventionshown in Fig. 2, and having a semicircular bar H6 of magnetic material,which is permanently magnetized in a manner similar to the permanentmagnet referred to in connection with the embodiment of the inventionshown in Fig. 2. The permanent magnet ||6 will thus operate to retardmovement of contact rod during interruption of high current arcs, andwill have substantially no retarding effect on contact rod 90 duringinterruption of low currents substantially in the same manner aspermanent magnet 80 described above in connection with the form ofinvention illustrated in Figs. 1, 2 and`3.

It is believed apparent from the foregoing that this invention providesfor most efficient arc extinction irrespective of the current magnitudeof the arc, by permitting extremely fast arc lengthening when arcs ofrelatively low current value are being interrupted, and automaticallyretarding arc lengthening when arcs of higher current value are beinginterrupted.

Having described preferred embodiments of the invention in accordancewith the `patent statutes, it is desired that the invention be notlimited to any particular form of electric circuit interrupter, inasmuchas it is demonstrated that it is applicable to different types` ofinterrupters, and accordingly it is desired that the invention beinterpreted as broadly as possible.

I claim as my invention:

l. An electric circuit interrupter comprising, separable arcingterminals, Ameansfor'striking only a single arc and separating saidarcing terminals, a speed retarding device for one of Vsaid arcingterminals, and said speed retarding device including a magneticelemcntresponsive to the magnitude of arc current for determining vthe rate atwhich said arcing terminals separate.

2. An electric circuit interrupter comprising, separable contacts, meansfor striking only a single arc and separating said contacts, a speedretarding device for one of said contacts, and said speed retardingdevice including a magnetic element responsive to the magnitude of arccurrentV for determining the rate at which said contacts separate.

3. An electric circuit interrupter comprising, separable arcingterminals normally held adjacent each other, means biasing at least oneof said arcing terminals for rapid separation movement, means forVreleasing ,said terminals and causing only a single arc to be formedbetween said terminals, and current responsive braking means including amagnetic element for said one terminal so that its rate of separatingmovement will vary in accordance with the value oi current in thecircuit. f A

4. An electrical circuit interrupter comprising, separable arcingterminals normally held adjacent each other, means biasingrat least oneof said arcing terminals for rapid separation movement, frictionalbraking means located'adjacent said one arcing terminal, said one arcingterminal and braking means being relatively movable into and out ofbraking engagement, vmeans for releasing said terminals and causing anare to be formed between said terminals, and current responsivemeans-for causing relative movement of said one arcing terminal andAbraking-means into engagement so that separating-movement of said onearcing terminalv will vary in accordance with the value of current inthe circuit.

5. An electric circuit interrupter` comprising, separable arcingterminals normally held adjacent each other, means biasing at least oneof said arcing terminals for rapid separation movement, frictionalbraking means located adjacent said one arcing terminal, said one arcingterminal being mounted for movement into and out of engagement with saidbraking means, means for releasing said terminals and causing an laro tobe formed betweensaid terminals, and :current responsive means forcausing movement of said one arcing terminal into engagement with saidbraking means so that separating movement of said one arcing terminalwill vary in accordance with 'the value 'of current in the circuit.

6. An electric circuit interrupter comprising, separable arcingterminals normally held radjacent each athen-'means biasing atleast oneof saidarcing terminalsfor rapid separation movement,- frictionalbraking'means located adjacent said oner arcing terminal, said onearcing term'ihal and braking means being yrelatively movableirito andout oi braking engagement, means for releasing 4said--terminals Aandcausing an arc toib'el formed' betweensaid terminals; and currentresponsive electromagnetic means energized by the current in the circuitfor causing relative movement of said one arcing terminal and brakingmeans into engagement so that separating movement of said one arcingterminal will vary in accordance with the value of current in thecircuit.

7. An electric circuit interrupter comprising, separable arc terminalsone of which is at one end of an elongated terminal support which inturn is mounted for generally longitudinal movement toward and away fromthe other oi said arc terminals and for limited lateral movement, meansbiasing said movable terminal for rapid separation movement, means forreleasing said terminals and causing an arc to be formed be- 'tween saidterminals, a frictional brake member positioned adjacent to one side ofthe path ofv longitudinal movement of said terminal support, meansresponsive to the current in the circuit for moving said terminalsupport laterally into engagement With said brake member so that therate of separating movement of said movable arc terminal will depend onthe magnitude of current being interrupted.

8. An electric circuit interrupter comprising, separable arc terminalsone or" which is at one end of an elongated terminal support which inturn is mounted for generally longitudinal movement toward and away fromthe other of said arc terminals and for limited lateral movement,` meansbiasing said movable arcing terminalfor rapid separation movement, meansfor releasing said terminals and causing an arc to be formed betweensaid terminals, said terminal support being of electrical conductingmaterial and serving to conduct current to. said movable arcingterminal, a frictional brake member positioned adjacent to one side ofthe path of longitudinal movement of said terminal support, meansproducing a` magnetic field passing through said terminal support tocause the latter to be moved laterally into engagement with said brakemember with a force determined by the magnitude of current beinginterrupted.

9.,An electric circuit interrupter comprising, separable arc terminalsone of which is 'at one end of an elongated terminal support which" inturn is mounted for generally longitudinal movement toward and away fromthe other o1" said arc terminals and for limited lateral movement, meansbiasing said movable arcing terminal for rapid separation movement,means for releasing said terminals and causing an arc to be formedbetween" said terminals, said terminal support being of electricalconducting material and serving to conduct current'to said movablearcingterminal, a frictional brake member positioned adjacent to one sideofthe path of longitudinal movement of said terminal support, apermanent magnet located so that its magnetic field passes through saidterminal support to cause the latter to be moved laterally intoengagement with said brake member with a force determined by themagnitude of current being interrupted.

10." An electric circuit interrupter comprising,- separable arcterminals one of which is at one end of an elongated terminal supportwhich inv turn is mounted for generally longitudinalmovement toward andaway from the other or said arc terminals and for limited lateralmovement, means biasing said movable arcing terminal for rapidseparation movement, means for releasingl saidA terminals and causing anarc tobe :formedl between' said terminals, said terminal -support beingof electrical conducting material and serving to conduct current to saidmovable arcing terminal, a frictional brake member positioned adjacentto one side of the .path of longitudinal movement of said terminalsupport, an electromagnet energized by current iiow in said terminalsupport and located so that its magnetic iield passes through saidterminal support to cause the latter to be moved laterally intoengagement with said brake member with a force determined by themagnitude of current being interrupted. t

l1. An electric circuit interrupter including means forming an elongatedarc passage of restricted cross-section, at least inner walls of saidpassage being of a material which evolves an arc extinguishing gas whenin proximity to an electric arc, a stationary arc terminal adjacent oneend of said are passage, an elongated arc terminal mounted for movementthrough said are passage, means biasing said movable terminal formovement in a direction away from said stationary terminal to rapidlyelongate an arc between said terminals, means normally holding saidmovable terminal at a position adjacent said stationary terminal, meansfor releasing said holding means, a brake member positioned adjacent oneside of said movable terminal at least during an initial part of itsmovement under the influence of said biasing means. and means responsiveto the magnitude of current flow in the circuit for moving said movableterminal laterally into engagement with said brake member with a forceproportional to current magnitude.

l2. A circuit interrupter having a pair of separable arcing terminalsbetween which an arc may be established and lengthened, braking meansincluding a relatively stationary brake part and a movable brake part,one of the separable arcing terminals being movable and causing movementof the movable brake part during the opening operation, means responsiveto the magnitude of the arc current for causing a greater interactionbetween the relatively.; stationary brake part and the movable brakepart during high current interruption than during low currentinterruption, and the braking means thereby acting to reduce the speedof separation between the arcing terminals during high currentinterruption.v

13. A-.circuit interrupter having a pair of separable arcing terminalsbetween .which an arc may be established and lengthened, braking meansincluding a relatively stationary brake part and a movable brake part,one of the separable arcing terminals being movable and causing movementof the movable brake part during the opening, operation, electromagneticmeans responsive to the magnitude of the arc current for causing agreater interaction between the relatively stationary brake part and themovable brake part during high current interruption than during lowcurrent interruption, and the braking meansY thereby acting to reducethe Vspeed of separation between the arcing terminals during highcurrent interruption.

1,4. A circuit interrupter having a pair of separableV arcing terminalsbetween which an arc may be established and lengthened, braking meansincluding a relatively stationary brake part and a cooperablefrictionally engageable movable brake part, one of the separable arcingterminals being movable and causing movement of the movable brake partduring the opening operation, electromagnetic means responsive to themagnitude of the arc current for causing a greater mechanical frictionalengagement between the cooperable relatively stationary and movablebrake parts during high current interruption than during low currentinterruption, and the braking means thereby acting to reduce the speedof separation between the arcing terminals during high currentinterruption.

ANDREW W. EDWARDS.

REFERENCES CITED UNITED STATES PATENTS Name Date Wallace Mar. 17, 1942Number

